infiltrate
Americanverb (used with object)
-
to filter into or through; permeate.
-
to cause to pass in by filtering.
-
to move into (an organization, country, territory, or the like) surreptitiously and gradually, especially with hostile intent.
The troops infiltrated the enemy lines.
-
to pass a small number of (soldiers, spies, or the like) into a territory or organization clandestinely and with hostile or subversive intent.
The intelligence agency infiltrated three spies into the neighboring country.
verb (used without object)
-
to pass into or through a substance, place, etc., by or as by filtering.
-
Pathology. to penetrate tissue spaces or cells.
noun
-
something that infiltrates.
-
Pathology. any substance penetrating tissues or cells and forming a morbid accumulation.
verb
-
to undergo or cause to undergo the process in which a fluid passes into the pores or interstices of a solid; permeate
-
military to pass undetected through (an enemy-held line or position)
-
to gain or cause to gain entrance or access surreptitiously
they infiltrated the party structure
noun
-
something that infiltrates
-
pathol any substance that passes into and accumulates within cells, tissues, or organs
-
pathol a local anaesthetic solution injected into the tissues to cause local anaesthesia
Other Word Forms
Derived Forms
Inflected Forms
Participles
Conjugated Forms
Present
-
infiltratesimple
-
infiltratessimple
-
have infiltratedperfect
-
has infiltratedperfect
-
am infiltratingprogressive
-
are infiltratingprogressive
-
is infiltratingprogressive
-
have been infiltratingperfect progressive
-
has been infiltratingperfect progressive
Past
-
infiltratedsimple
-
had infiltratedperfect
-
was infiltratingprogressive
-
were infiltratingprogressive
-
had been infiltratingperfect progressive
Future
Etymology
Origin of infiltrate
Explanation
If you infiltrate a group or organization, you join it in order to gain information, like an employee of a donut shop that infiltrates the competition to try to learn its "secret recipe" for its delicious dough. Infiltrate is a verb that is familiar to international spies and undercover agents, who are all adept at joining a group under false pretenses, fitting in, and working their way up to the highest ranks in order to find out as much information as they can about the group. The word can be used more broadly to describe anything that stealthily becomes a part of something else, such as slang words that infiltrate our everyday speech.
Vocabulary lists containing infiltrate
A Separate Peace
Looking to grow your vocabulary? Check out this interactive, curated word list from our team of English language specialists at Vocabulary.com – one of over 17,000 lists we've built to help learners worldwide!
Vocabulary: A Rapper's Delight!
Interested in learning more words like this one? Our team at Vocabulary.com has got you covered! You can review flashcards, quiz yourself, practice spelling, and more – and it's all completely free to use!
While the World Watched
Want to remember this word for good? Start your learning journey today with our library of interactive, themed word lists built by the experts at Vocabulary.com – we'll help you make the most of your study time!
Example Sentences
Examples are provided to illustrate real-world usage of words in context. Any opinions expressed do not reflect the views of Dictionary.com.
See Examples For:
The army has been sending in small groups of soldiers to infiltrate and secure positions, a method previously used to capture the Ukrainian city of Pokrovsk in late 2025.
From Barron's ● Jul. 4, 2026
He used his vast fortune to infiltrate American higher education institutions by positioning himself as a major donor to scientists.
From The Wall Street Journal ● Jun. 17, 2026
While seizing on a story about Manhattanites living in storage facilities, he meets Virginia, with whom he concocts a plan to infiltrate a massive Oklahoma data center.
From Los Angeles Times ● May 12, 2026
When HOXD13 was turned off, more T cells were able to infiltrate tumors.
From Science Daily ● Apr. 21, 2026
Brown was a union worker and a former Klan official who had changed his ways and offered to infiltrate the Klan.
From "Freakonomics: A Rogue Economist Explores the Hidden Side of Everything" by Steven D. Levitt
The Interior Ministry, with an estimated 140,000 state security officials and 500,000 informants, monitors and infiltrates dissident movements.
From The Wall Street Journal ● Jul. 5, 2026
The stakes around AI are rising as it infiltrates every aspect of the economy.
From Los Angeles Times ● Mar. 5, 2026
"When corruption infiltrates the sport, it brings disgrace not only to the participants but damages the public trust in an institution that is vital and dear to all of us."
From Barron's ● Nov. 9, 2025
These deadly puzzles have already reeled in Holmes when the very American Amelia infiltrates 221B Baker Street, claiming to be his daughter.
From Salon ● Apr. 16, 2025
Cancerous tissue thus propagated presents all the characteristic features of the malignant growth of sporadic tumours; it infiltrates and produces extensive secondary growths.
From Encyclopaedia Britannica, 11th Edition, Volume 5, Slice 2 "Camorra" to "Cape Colony" by Various
He acknowledged that Russian troops have tried to seize the town and had infiltrated it in small groups.
From Barron's ● Jul. 4, 2026
It was set up after senior police officer Lt-Gen Nhlanhla Mkhwanazi alleged last July that organised crime groups had infiltrated the government.
From BBC ● Jun. 25, 2026
Turning Robin Hood into a conflicted antihero suggests society has been infiltrated by cynicism about anyone being able to save us.
From The Wall Street Journal ● Jun. 23, 2026
Epstein’s network had infiltrated the boardrooms of hundreds of major U.S. companies, with clear consequences for corporate misconduct affecting employees and the broader business culture.
From Salon ● Jun. 20, 2026
“There’s no reason to think they haven’t infiltrated organizations on both sides of the war.”
From "Hollow City" by Ransom Riggs
He admitted that small groups of Russian troops have been infiltrating the town but insisted that fighting was ongoing.
From Barron's ● Jul. 4, 2026
“They’re infiltrating, pretending they’re parents or they know people, but I’m the mom. I know who they are.”
From Los Angeles Times ● May 14, 2026
In Jihad in America, Emerson used hidden-camera footage to try to build a case that jihadists were infiltrating Middle America.
From Slate ● Apr. 19, 2026
Legacy food makers and buzzy upstarts are infiltrating households with many new condiments.
From The Wall Street Journal ● Apr. 17, 2026
MK had been slowly infiltrating men back into the country with forged identity documents.
From "Long Walk to Freedom" by Nelson Mandela
Definitions and idiom definitions from Dictionary.com Unabridged, based on the Random House Unabridged Dictionary, © Random House, Inc. 2023
Idioms from The American Heritage® Idioms Dictionary copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.
